Over-based, oil-soluble magnesium salts of sulphonic acids are used as additives in oil-based compositions, such as lubricants, greases, fuels, and the like. They function as detergents and acid neutralizers, thereby reducing wear and corrosion and extending the engine life.
Highly basic magnesium salts of a sulphonic acid having a metal ratio of equivalents of magnesium to equivalents of sulphonic acid ranging from 10 up to 40 or more, particularly the higher metal ratios of 20 to 40 have been difficult to prepare in a one-step operation using MgO as a Mg source. In systems previously described, either insufficient magnesium was dispersed or an unfiltered product resulted.
It has been discovered that over-based magnesium sulphonates may be prepared in a one-step operation by using a reaction promotor system comprising (1) a carboxylic compound selected from the group of compounds consisting of lower carboxylic acids, lower carboxylic anhydrides, substituted lower carboxylic acids, metal salts and esters of lower carboxylic acids and mixtures thereof, all having from 1 to 5 carbon atoms; (2) water and optionally (3) an alcohol selected from the group of compounds consisting of lower alkanols, lower alkoxy alkanols and mixtures thereof, all having from 1 to 5 carbon atoms. Such a promotor system gives a high quality over-based magnesium sulphonate having very high metal ratios which is suitable for use in various types of oil-based compositions.
It is therefore an object of the invention to provide a process for manufacturing oil-soluble, over-based magnesium salts of sulphonic acids having metal ratios ranging from 5 and upwards to 40 or more where the product is prepared in a one-step operation of contacting the reaction mixture with an acidic gas.
It is a further object of the invention to provide a reactor promoter system for use in processes for manufacturing oil-soluble, over-based magnesium salts of sulphonic acids having metal ratios of 10 up to 40 or more.
It is another object of the invention to provide a process for preparing a magnesium salt of a sulphonic acid having very high metal ratios wherein over-basing of the sulphonic acid is accomplished by using a promoter system in combination with a light form of magnesium oxide.